The inventors of the present invention have proposed an interface circuit for converting binary signals to multi-level signals as well as for converting multi-level signals to binary signals in the Japanese patent application Hei 04-301740 and U.S. patent application Ser. No. 08/228,903. This circuit converts a binary signal into a multi-level signal and transmits the result to another device. The multi-level signal is converted by the interface circuit into a binary signal again in the latter device. This circuit has a problem that a divider circuit is used consisting of a plurality resisters serially connected. The circuit consumes a lot of electrical power.